A number of dinoflagellate species are known to produce potent neurotoxins. Their blooms are commonly referred to as ''red tides.'' An understanding of the genetic regulatory mechanisms that affect bloom growth and, in particular, the development of biomarkers to assess bloom growth status is essential for the development of scientifically sound management and mitigation policies. The genetic organization and regulation of these organisms has been shown to be distinct from non-protist eukaryotes. Dinoflagellates are remarkable for their extremely large genomes that show little transcriptional regulation and with genes present as multiple tandem copies that are polycistronically processed through coupled trans-splicing and polyadenylation. A broad range of investigations has implicated mRNA recruitment as a major site of regulation of gene expression. However, relatively little is understood regarding translational initiation and its regulation in these organisms. The goal of this application is to unravel the roles of the likely key players in translational regulation, eIF2 and eIF4, along with the spliced leader cap structures in regulating gene expression. Using the icthyotoxic dinoflagellate, Karlodinium veneficum and the toxin producing Karenia brevis, the investigators will a) determine whether changes in eIF2-alpha phosphorylation underlie dial changes in gene expression or responses to different stressors; b) begin characterization of the eIF2-alpha-kinases from K. veneficum; c) characterize the ability of K.veneficum eIF4E family member to bind to cap structures and translational binding partners; d) assess the role of K.veneficum eIF4E members in mRNA recruitment. The investigators current understanding of translational regulation is derived mainly from studies in mouse, yeast and plants and does not allow for the diversity of eukaryotic life, the bulk of which is to be found in the Protista. The investigators' results are expected to define a new paradigm for translational regulation in dinoflagellates and represent an innovative approach to increase our understanding of the translational process itself as well as to bridge the gap between genomics and physiological complexity in dinoflagellates. Given the central role of translation in dinoflagellate gene expression, this will provide critical insight into mechanisms relevant to dinoflagellate growth, toxicity, and the regulation of harmful algal blooms. Public Health Relevance: A number of dinoflagellate species are known to produce potent neurotoxins. Their blooms are commonly referred to as ''red tides.'' The investigators are studying the mechanisms by which these organisms can regulate their growth and respond to the environment. Because of their unique genome structure, dinoflagellates regulate themselves in unusual ways. The studies proposed here will provide critical insight into mechanisms relevant to dinoflagellate growth, toxicity, and the regulation of harmful algal blooms, with a lon term goal of providing avenues for intervention.